Investments - Summary of Realized and Unrealized Gains and Losses on Equity Investments Recognized in Investment and Other Income in Consolidated Statements of Operations (Details) $ in Millions	12 Months Ended
Dec. 31, 2018 USD ($)
Equity Securities Fv Ni Gain Loss Alternative [Abstract]
Net gain on equity securities	$ 11.8
Less: net gain recognized on equity securities sold	(2.4)
Unrealized net gain recognized on equity securities still held at the reporting date	$ 9.4

Amount of unrealized and realized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=84241550&loc=SL75117546-209714

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- Definition

Amount of realized gain (loss) from sale of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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- Definition

Amount of unrealized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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